Root responses to cereal cyst nematode (Heterodera avenae) in hosts with different resistance genes

Abstract

The development of cereal cyst nematode (CCN ; Heterodera avenae) induced syncytia in the host roots of infected resistant bread wheat (Triticum aestivum cv. AUS10894), diploid wheat (Aegilops tauschii), barley (Hordeum vulgare cv. Chebec and cv. Galleon) and in the susceptible wheat cv. Meering and barley cv. Clipper were studied over a period of 13 d. The resistance to CCN in these cereal plants is conferred by the resistance genes Cre1 in the wheat cv. AUS10894, Cre3 in A. tauschii, Ha2 in barley cv. Chebec and Ha4 in barley cv. Galleon. Anatomical observations were made on the development of the syncytia in CCN-infected wheat and barley roots, which carry each of these four sources of resistance genes. Accelerated development of the syncytia in resistant plants, especially in the barley cultivars, was observed. The sites of syncytia development in susceptible wheat and barley were also closely associated with the vascular tissues in the stele, but less so in the resistant plants. The syncytia in the infected susceptible wheat and barley were also metabolically active at day 13. By contrast, the syncytia of resistant wheat plants carrying the Cre1 or Cre3 genes remained extensively vacuolated and less metabolically active. In barley plants with the Ha2 or Ha4 genes, the syncytia appeared non-functional and in early stages of degeneration by day 13 after inoculation.

The dynamics of cereal cyst nematode infection differ between susceptible and resistant barley cultivars and lead to changes in (1,3;1,4)‐β‐glucan levels and HvCslF gene transcript abundance

“…Previous observations have indicated that the timing of syncytial development varies among barley cultivars (Seah et al ., ). Here, differences between susceptible and resistant plants were observed as early as 4 DAI.…”

“…Of these, Rha2 and Rha4 are effective against the H. avenae pathotype in Australia and have been extensively used in barley breeding. A comparative histological study of infected barley roots suggested that syncytium development in the CCN‐resistant cultivars Chebec ( Rha2 ) and Galleon ( Rha4 ) takes place earlier than that in the susceptible cultivar Clipper (Seah et al ., ). Moreover, it was found that the degradation of syncytia occurs earlier in Galleon than in Chebec, indicating that barley cultivars carrying different resistance genes may employ different resistance mechanisms.…”

Spring Wheat Tolerance and Resistance to Heterodera avenae in the Pacific Northwest

“…The juveniles successfully penetrate roots in equal numbers for resistant as well as susceptible cultivars (35,38). Cells of the syncyfium develop but then quickly deteriorate in resistant cultivars, causing death or suppressed reproductive capacity of the female associated with the deteriorated syncytium (7,42). Cells of the syncyfium develop but then quickly deteriorate in resistant cultivars, causing death or suppressed reproductive capacity of the female associated with the deteriorated syncytium (7,42).…”

Molecular characterization and functional analysis of two new β‐1,4‐endoglucanase genes (Ha‐eng‐2,Ha‐eng‐3) from the cereal cyst nematode Heterodera avenae

“…To degrade cell walls, plant‐parasitic nematodes secrete various types of cell wall‐degrading enzymes and exert mechanical force by stylet thrusting. β‐1,4‐endoglucanases were the first cell wall‐degrading enzymes to have been identified in two cyst nematode species more than a decade ago (Smant et al ., ) and have subsequently been detected in different plant‐parasitic nematodes (Hassan et al ., ). Most of these identified β‐1,4‐endoglucanases (EC 4.2.1.4) belong to the glycosyl hydrolase family 5 (GHF5) and show high similarity with bacterial cellulases (Mayer et al ., ).…”